In X-ray photography for medical use, in recent years, an X-ray imaging system using an X-ray image pickup apparatus in place of an X-ray sensitive film has been extensively used. Such an X-ray imaging system does not require development like that for an X-ray sensitive film, and is highly convenient in the point that it is possible to confirm an X-ray image in real time or the like, that also has superior points in aspects of data storage quality and data handling facilitation. In X-ray photography for dental diagnosis, also, such an X-ray imaging system has been used in various types of imaging modes, such as panoramic radiography, cephalometrical radiography, and CT scan.
In the case of a dental X-ray image pickup system, in some cases, the shape of an imaging area required for an X-ray image pickup apparatus differs according to various types of imaging modes described above. That is, a longitudinally sufficient width is required for an imaging area used for panoramic radiography or cephalometrical radiography. Further, a laterally sufficient width is required for an imaging area used for CT scan, and a certain measure of width is required therefor in a longitudinal direction as well. However, when a plurality of X-ray image pickup apparatuses meeting these requirements are made available, problems that the X-ray image pickup system is increased in size or it is necessary to exchange an X-ray image pickup apparatus at the time of changing an imaging mode, which takes time and labor, are brought about. Accordingly, it is preferable that one X-ray image pickup apparatus is capable of resolving these requirements for an imaging area.
For example, in Patent Document 1, there is disclosed a dental diagnosis X-ray image pickup apparatus equipped with an X-ray generator and an X-ray detector. In this X-ray image pickup apparatus, an X-ray is radiated via a narrow groove-like slit or a rectangular slit in order to be capable of selectively switching to generate an X-ray narrow slit beam and an X-ray broad beam. An X-ray narrow slit beam is used for panoramic radiography, cephalometrical radiography, or the like, and an X-ray broad beam is used for CT scan or the like. Then, in this Patent Document 1, there is described that both of an X-ray narrow slit beam passing through a narrow groove-like slit and an X-ray broad beam passing through a rectangular slit are taken as images by one solid-state image pickup element.
Further, as a solid-state image pickup apparatus used for such an X-ray image, pickup system for medical use, solid-state image pickup apparatuses using the CMOS technology are known, and a solid-state image pickup apparatus of a passive pixel sensor (PPS: Passive Pixel Sensor) system among those is known. A solid-state image pickup apparatus of a PPS system is equipped with a photodetecting section in which PPS-type pixels including photodiodes for generating charges according to incident light intensities are two-dimensionally arrayed in M rows and N columns, and charges generated in the photodiodes according to light incidence in the respective pixels are accumulated in capacitors in integrating circuits, and voltage values corresponding to the quantities of accumulated charges are output.
Generally, the respective output terminals of M pixels on each column are connected to an input terminal of an integrating circuit provided so as to correspond to the column via a readout wiring provided so as to correspond to the column. Then, the charges generated in the photodiodes in the respective pixels pass through the readout wiring corresponding to the column, and are input to the integrating circuit in series for each row of the first row to the M-th row, and voltage values corresponding to the quantities of charges are output.